Non-contact processing of crystal materials

Abstract

A system and method for forming spherical semiconductor crystals is disclosed. The system includes a receiver tube 18 for receiving semiconductor granules 104. The granules are then directed to a chamber 14 defined within an enclosure 20. The chamber maintains a heated, inert atmosphere with which to melt the semiconductor granules into a molten mass. A nozzle, 40, creates droplets from the molten mass, which then drop through a long drop tube 16. As the droplets move through the drop tube, they form spherical shaped semiconductor crystals 112. The drop tube is heated and the spherical shaped semiconductor crystals may be single crystals. An inductively coupled plasma torch positioned between the nozzle and the drop tube melts the droplets, but leaving a seed in-situ. The seed can thereby facilitate crystallization.

What is claimed is: 
     
       1. An apparatus for forming spherical shaped semiconductor crystals, the apparatus comprising: a receiver tube for receiving semiconductor granules;   a chamber for receiving the semiconductor granules from the receiver tube;   a heater for heating the semiconductor granules inside the chamber into a molten mass;   a nozzle located at one end of the chamber;   a drop tube connected to the nozzle; and   an inductively coupled plasma torch positioned adjacent to the drop tube,   wherein droplets from the molten mass can be formed by the nozzle and dropped through the drop tube, thereby forming the spherical shaped semiconductor crystals.   
     
     
       2. The apparatus of claim 1 further comprising: an enclosure for maintaining an inert atmosphere, wherein the chamber is defined within the enclosure.   
     
     
       3. The apparatus of claim 1 further comprising: one or more heaters for heating an interior portion of the drop tube.   
     
     
       4. The apparatus of claim 3 wherein the crystals produced from the drop tube are coarse grained. 
     
     
       5. The apparatus of claim 1 wherein a portion of the inductively coupled plasma torch is positioned between the nozzle and the drop tube. 
     
     
       6. The apparatus of claim 1 wherein the inductively coupled plasma torch is housed in a quartz tube that is further connected to the drop tube. 
     
     
       7. A method for forming spherical shaped semiconductor crystals, the method comprising: receiving semiconductor granules into a chamber;   heating the semiconductor granules inside the chamber into a molten mass;   forming droplets of the molten mass using a nozzle located at one end of the chamber;   moving the droplets through a tube connected to the nozzle; and   providing an inductively coupled plasma torch adjacent to the tube,   wherein the droplets become the spherical shaped semiconductor crystals as they move through the tube.   
     
     
       8. The method of claim 7 further comprising: maintaining an inert atmosphere for the chamber.   
     
     
       9. The method of claim 7 further comprising: heating an interior portion of the tube to slow a rate at which the droplets become the spherical shaped semiconductor crystals.   
     
     
       10. The method of claim 9 wherein the spherical shaped semiconductor crystals produced from the tube are coarse grained. 
     
     
       11. The method of claim 7 wherein a portion of the inductively coupled plasma torch is positioned between the nozzle and the tube so that the droplets are preheated by the portion. 
     
     
       12. The method of claim 7 wherein the inductively coupled plasma torch is housed in a quartz tube that is positioned between the nozzle and the tube. 
     
     
       13. A method of making a spherical shaped crystal, the method comprising the steps of: receiving a first polycrystal granule;   melting the first polycrystal granule into a seed and a first molten mass; and   solidifying the first molten mass using the seed, wherein the first molten mass creates crystalline directions identical to those of the seed and the solidifying occurs in a non-contact environment.   
     
     
       14. The method of claim 13 further comprising the steps of: receiving a second polycrystal granule, the second polycrystal having a relatively high number of crystalline directions;   coating the second polycrystal granule with a nucleating agent;   completely melting the coated second polycrystal granule into a second molten mass; and   solidifying the second molten mass to form the first polycrystal granule.   
     
     
       15. The method of claim 14 wherein the first polycrystal granule has a relatively low number of crystalline directions. 
     
     
       16. The method of claim 14 wherein the step of completely melting the coated second polycrystal granule includes levitating the second polycrystal granule in a non-contact container. 
     
     
       17. The method of claim 13 wherein the seed and the spherical shaped crystal are both single crystals. 
     
     
       18. The method of claim 13 wherein the step of melting occurs without physical contact with the first polycrystal granule. 
     
     
       19. A system for making a spherical shaped single crystal, the system comprising: means for receiving a first polycrystal granule;   means for melting the first polycrystal granule into a seed and a first molten mass; and   a non-contact environment for solidifying the first molten mass using the seed, wherein the first molten mass creates crystalline directions identical to those of the seed.   
     
     
       20. The system of claim 19 further comprising: means for receiving a second polycrystal granule, the second polycrystal having a relatively high number of crystalline directions;   means for coating the second polycrystal granule with a nucleating agent;   means for melting the coated second polycrystal granule into a second molten mass; and   means for solidifying the second molten mass to form the first polycrystal.   
     
     
       21. The system of claim 20 wherein the means for melting the coated second polycrystal granule and the means for melting the first polycrystal granule share a common structure. 
     
     
       22. The system of claim 20 wherein the first polycrystal granule has a relatively low number of crystalline directions. 
     
     
       23. The system of claim 20 wherein the means for melting the coated second polycrystal granule includes means for levitating the second polycrystal granule in a non-contact manner. 
     
     
       24. The system of claim 20 wherein the seed and the spherical shaped crystal are both single crystals. 
     
     
       25. The system of claim 19 wherein the means for melting never physically contacts the first polycrystal granule. 
     
     
       26. A method of making a spherical shaped silicon crystal, the method comprising the steps of: forming a small single crystal particle;   applying a silicon vapor to the single crystal particle to form a silicon granule with a single crystal core;   melting the silicon granule into a seed and a first molten mass, the seed being formed from the single crystal core; and   solidifying the first molten mass using the seed, wherein the first molten mass creates crystalline directions identical to those of the seed and the solidifying occurs in a non-contact environment.   
     
     
       27. The method of claim 26 wherein the small single crystal particle is formed using epitaxial growth. 
     
     
       28. The method of claim 26 wherein the step of applying a silicon vapor utilizes a fluid bed reactor. 
     
     
       29. The method of claim 26 wherein the spherical shaped crystal is a single crystal. 
     
     
       30. The method of claim 26 wherein the step of melting occurs without physical contact with the silicon granule. 
     
     
       31. The method of claim 26 further comprising: heating the small single crystal particle before applying the silicon vapor.